Outlook Calendar ItemIds are different for Appointment Organizer and Appointment Attendee

Question

We are developing an Addin for Outlook Calendar using Office JS, such Addin being used by both Organizers and Attendees, using the same Taskpane JS code. We need thus to obtain a unique UID for the same appointment.

As documented,

• as Organizer using the Office.AppointmentCompose interface we use the method getItemIdAsync, i.e., Office.context.mailbox.getItemIdAsync and only after saving the Item for the ItemId to be available, and
• as Attendee using the Office.AppointmentRead interface we use the property ItemId, that is, Office.context.mailbox.item.itemId

But they are not the same!

In the Addin JS code of the Attendee, how can I identify the ItemId of the Organizer of the appointment, in which the Attendee was invited for?

How can we have a common UID for Organizer and Attendee? Is there a EWS request I can make with Office.context.mailbox.makeEwsRequestAsync? Which XML request code then?

Answer 1

The appointment uid is exposed in both EWS (UID property) and in Graph (uid property). They will be the same for both the organizer and the attendee.